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Organizers of the Primary Production Algorithm Round Robins (PPARR) -5,
which will focus on the Arctic Ocean, invite community participation.
This opportunity is open to those who use models to estimate marine
photosynthesis, want to quantify the performance of their model in the
Arctic Ocean and/or compare their model to others.

Estimations, based on remote sensing observations, indicate that primary
productivity (PP) in the Arctic Ocean has increased considerably in the
last decade. However, consensus about the relative importance of
variables and processes controlling PP in the Arctic Ocean at different
times and in different regions is lacking. Sea ice, colored dissolved
organic matter, persistent cloud cover, and stratification are major
controls of the light regime for phytoplankton while winter wind mixing,
upwelling, eddies, river discharge, and stratification are involved in
nutrient replenishment.

With funding from NASA's Ocean Biology and Biogeochemistry Program, the
PPARR-5 study will compare models that estimate primary productivity in
the Arctic Ocean from either ocean-color based models, biogeochemical
ocean circulation models, or earth system models. This project continues
on four previous PPARR comparison studies and will be the first one to
focus on the Arctic Ocean. PPARR-4 included over 50 investigators.

PPARR-5 will include comparisons to high quality in situ primary
productivity data over a broad array of locations, which will allow a
comprehensive assessment of model estimates of primary productivity and
their associated uncertainties. Input data; including chlorophyll, SST,
PAR, and mixed layer depth for specific locations and dates; will be
provided by the organizers to the participating modeling groups. The
modeling groups will estimate integrated net primary productivity and,
if possible, depth-resolved profiles of primary production and
chlorophyll a. These results will be sent back to the organizers, who
will compare and analyze the results. Distribution of the PPARR-5 Arctic
Ocean data set will begin in mid-March.

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